Single proton structure ofIr193,195,197and perturbed spin(6) symmetry

Abstract

The $^{194,196,198}\mathrm{Pt}(\stackrel{\ensuremath{\rightarrow}}{t}, \ensuremath{\alpha})^{193,195,197}\mathrm{Ir}$ reactions have been studied with a 17 MeV polarized triton beam. Based on the measured angular distributions of cross sections and analyzing powers, several new ${I}^{\ensuremath{\pi}}$ assignments were made in $^{195}\mathrm{Ir}$ and new levels were identified in $^{197}\mathrm{Ir}$. The change in the distribution of ${d}_{\frac{3}{2}}$ spectroscopic strength as a function of neutron number is observed to be quite dramatic. Two large fragments are observed in $^{193}\mathrm{Ir}$, all of the ${d}_{\frac{3}{2}}$ strength is concentrated in the ground state of $^{197}\mathrm{Ir}$, and $^{195}\mathrm{Ir}$ shows a situation intermediate between these two. The empirical ${d}_{\frac{3}{2}}$ strength in $^{193}\mathrm{Ir}$ is well reproduced by the predictions of the $\mathrm{U}(\frac{6}{4})$ supersymmetry proposed for the Os-Ir-Pt nuclei. The change in the ${d}_{\frac{3}{2}}$ strength as a function of neutron number is well reproduced by a perturbation of this symmetry.NUCLEAR REACTIONS $^{194,196,198}\mathrm{Pt}(\stackrel{\ensuremath{\rightarrow}}{t}, \ensuremath{\alpha})$, ${E}_{t}=17$ MeV, enriched targets; measured $\ensuremath{\sigma}({E}_{\ensuremath{\alpha}}, \ensuremath{\theta})$, ${A}_{y}({E}_{\ensuremath{\alpha}}, \ensuremath{\theta})$. $^{193,195,197}\mathrm{Ir}$ deduced levels, $I$, $\ensuremath{\pi}$, spectroscopic strengths.NUCLEAR STRUCTURE Interacting boson fermion model, $\mathrm{U}(\frac{6}{4})$ supersymmetry, spin(6) symmetry.